The present invention relates to spray drying of food powders and more particularly to an improved mechanism and method for spray drying of food powders result in agglomeration of the dried food powders.
Many spray dried food powders do not disperse readily in water. They may also be dusty and not very free-flowing. Agglomeration of dried food powders is a means for giving the product good dispersing and dissolving properties, making the product free-flowing and reducing its dustiness. It has been found that conventional agglomerating procedures produce a considerable number of fine powder which must be sifted away from the agglomerates. Moreover, the agglomerated food powders formed are not of a uniform size. In addition, a number of oversized particles are produced by existing mechanism which must be removed and separated from the particles by a screen or some other means.
In several different kinds of existing agglomeration equipment, a two-step procedure is usually required whereby the powders are wetted in order to agglomerate the particles, and then the wetted particles are dried in separate equipment to the desired moisture level. Production of a higher percentage of oversized material and fine powder is the result of such procedures. These agglomerating procedures which use a one-step process, for example in a spray dryer, do not mix the powder with the agglomerating liquid sufficiently enough to give uniform sized agglomerates. In addition, too much fine powder, as well as too many coarse materials, are produced by such procedures. U.S. Pat. No. 3,621,902 shows hot air being blown against a spray of milk foam ejected from a nozzle which surrounds the spray nozzle. It is believed that the purpose is to produce powdered milk without any burnt particles. U.S. Pat. No. 4,640,839 shows an agglomeration process in which a powdered water-soluble material is agglomerated by projecting the material in a stream through a moistening zone and directing steam through it. U.S. Pat. No. 3,700,461 shows an agglomerator in which the material is wetted and suspended in a gaseous medium. U.S. Pat. No. 3,584,097 shows powder subjected to an upwardly flowing pulsating air stream and injected with a liquid binder. U.S. Pat. No. 4,042,653 shows an agglomerating process in which atomized droplets are dried and sprayed with a fluid binder. None of these prior patents disclose the invention which is disclosed and claimed herein.